The present invention relates to a substantially aqueous emulsion comprising a fluorocarbon silane or hydrolyzate thereof, or both; to a composition or product comprising the emulsion; and to a heat-resistant and/or water-repellent coated product comprising the composition.
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U.S. Pat. No. 5,550,184 discloses an emulsion containing a fluorocarbon silane hydrolyzed product and a surfactant for emulsifying the hydrolyzed product that does not require a special heat treatment and can provide the water repellency to the base material.
Japanese Kokai Patent Application Hei 11[1999]-181355 discloses an emulsion containing fluorocarbon silane hydrolyzed product, surfactant for emulsifying the hydrolyzed product, and specific silicate, in which pH is adjusted to 7 or more. A characteristics is that it can maintain an excellent water repellency even under a high-temperature condition, that is, heat resistance and water repellency can be provided to a base material.
Japanese Kokai Patent Application Hei 11[1999]-181355 disclose an emulsion containing a hydrolyzed product of a fluorocarbon silane emulsified with a specific nonionic surfactant and a specific silicate, and an emulsion in which pH is adjusted to 4 or more. The emulsion exhibits heat resistance and water repellency.
However, a coated layer containing these emulsions is not as durable as one skilled in the art would desire. Additionally, though these emulsions exhibit water-repellency characteristics, they do not exhibit oil-repellent property. For example, glass window of oven, range, or toaster can be coated with a layer formed by an emulsion having good water repellency at high temperature, but it has a poor oil-stain resistance. It is also highly desirable to develop an emulsion that can exhibit both water-repellent and oil-repellent properties for a variety of applications.
Therefore, there is an increasing need to develop a composition containing the emulsion for coating on glass windows of, for example, oven range and toaster as well as precision products related to automobiles. Also desired is an improved heat resistance, water repellency, and durability of the layer coated on the glass.
A product or composition comprises a substantially aqueous emulsion, which comprises, or is produced by combining, a fluorocarbon silane or hydrolyzate thereof; a surfactant, a silicon-containing compound, and optionally a film-forming agent wherein the film-forming agent is silicon dioxide, titanium dioxide, zirconium dioxide, organoalkoxysilane, polysilazane, or combinations of two or more thereof.
A product comprises, or is produced by combining, a substrate, an emulsion, and optionally an undercoat layer between the substrate and the emulsion wherein the emulsion comprises or is produced by combining a fluorocarbon silane or hydrolyzate thereof, a surfactant, and a silicon-containing compound; the silicon-containing compound is silicate, organoalkoxysilane, aminosilane, epoxysilane, mercaptosilane, or combinations of two or more thereof; and the undercoat layer comprises or is produced from at least one film-forming agent, which is silicon dioxide, titanium dioxide, zirconium dioxide, organoalkoxysilane, polysilazane, or combinations of two or more thereof.
The term xe2x80x9chydrolyzatexe2x80x9d is a hydrolyzed product of a fluorocarbon silane. The fluorocarbon silane can have the structure of Rfxe2x80x94(CH2)pxe2x80x94Si(xe2x80x94(Oxe2x80x94CH2CH2)nxe2x80x94ORxe2x80x2)3; Rf is a perfluoroalkyl group having 3 to 18 carbon atoms or a mixture of perfluoroalkyl groups having 3-18 carbon atoms; each Rxe2x80x2 can be the same or different and is independently an alkyl group having 1 to 3 carbon atoms; p=1-4 and n=2-10, all inclusive. When p and n are each 2, the fluorocarbon is preferably a perfluoroalkylethyl tris(2-(2-methoxyethoxy)ethoxy)silane, and when p is 2 and n is 3, it is preferably a perfluoroalkylethyl tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)silane. Such a fluorocarbon silane can be manufactured by any well-known method and commercially available. If two or more fluorocarbon silanes are used, they are generally mixed together.
The silicon-containing compound can be any silicon compound that is polymerizable and can produce an emulsion having the desired characteristics disclosed herein. The silicon compound can be copolymerized with the fluorocarbon silane hydrolyzed product to improve heat resistance and water repellency of the emulsion and the coating layer containing the emulsion.
The preferred silicon compounds include, but are not limited to, silicate, organoalkoxysilane compound, aminosilane compound, epoxysilane compound, mercaptosilane compound, and combinations of two or more thereof.
A preferred silicate can have the structure of Sixe2x80x94R4; R is at least one organic radical selected from a group consisting of OCH3, OCH2CH3, (OCH2CH2)mOCH3, and m=1-10. The more preferred silicate is Si((OCH2CH2)mOCH3)4 where m=1-3 for it is water soluble. The most preferred silicate is Sixe2x80x94((OCH2CH2)2OCH3)4.
A preferred organoalkoxysilane can have the structure of R1wSi(OR2)4xe2x88x92w; R1 and R2 are each independently one or more alkyl groups having 1-5 carbons; and w is a number from 1 to 3, inclusive. The most preferred organoalkoxysilane is organomethoxysilane.
A preferred aminosilane, epoxysilane, or mercaptosilane can have the formula of R3R4XSiR5y(OR6)3xe2x88x92(X+y); R3is a radical containing amino group, epoxy group, glycidoxy group, thiol group, or combinations of two or more thereof; R4, R5, and R6 can be the same or different and are each independently an alkyl group having 1-5 carbons or a mixture of the alkyl groups; x=0-1; y=0-1; and x+yxe2x89xa62. When R3 is an amino group, R4 can also be substituted by an amino group.
Specific examples of preferred aminosilane compounds include, but are not limited to, N-(2-aminoethyl) 3-aminopropylmethyl dimethoxysilane, N-(2-aminoethyl) 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, and combinations of two or more thereof.
Specific examples of preferred epoxysilane compounds include, but are not limited to, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyldimethoxysilane, and combinations thereof.
Specific examples of preferred mercaptosilane compound includes, but is not limited to, 3-mercaptopropyl trimethoxysilane.
When oil resistance and stain resistance are desired along with the heat resistance and the water repellency in the coated product, an organoalkoxysilane is preferable among the silicon compounds.
The silicon compound can be used at any amount effective to produce an emulsion having desired heat resistance and water repellency. Generally the mole ratio of a silicon compound to of the fluorocarbon silane or its hydrolyzed product can be in the range of from about 0.3:1 to about 10:1, preferably 0.3:1 to 5:1, and more preferably 0.4:1 to 2:1.
Any surfactant that can emulsify a fluorocarbon silane or its hydrolysis product can be used. The surfactant generally is a surfactant having an HLB value sufficiently high to inhibit self-condensation of the fluorocarbon silane hydrolysis product. The term xe2x80x9cHLBxe2x80x9d refers to the HLB system published by ICI America""s, Inc., Wilmington, Del.; Adamson, A. W., xe2x80x9cPhysical Chemistry of Surfacesxe2x80x9d, 4th edition, John Wily and Sons, New York, 1982). The surfactant can be anionic, cationic, nonionic, amphoteric, or combinations thereof. The preferred surfactants are those with HLB values greater than 12, more preferably greater than 16. Generally, the lower HLB value the surfactant is, the larger amount of the surfactant is required to stabilize the emulsion. Two or more miscible surfactants generally can also be combined or mixed for use as long as they have HLB values sufficiently high to inhibit self-condensation of the fluorocarbon silane or its hydrolyzate products. Two or more kinds of surfactants that are compatible can also be used by mixing.
The HLB value of a nonionic surfactant can be determined by calculation with a formula, among others, originated by Griffin of Atlas Co. (now ICI America) in the U.S. In the case of anionic or cationic surfactant, a method for determination by calculation of the HLB value is not available to date. Nevertheless, paying attention to the fact that changes in emulsification characteristics are sensitive to changes in the HLB value, Atlas Company established and published a method for the experimental determination of the HLB value by an emulsification experiment on standard oil. Companies other than Atlas have also established methods for experimental determination of HLB value. However, it can be clarified by the adoption of any experimental method that the HLB value of the anionic type or the cationic type is greater than 16.
Examples of nonionic surfactants include, but are not limited to, Rfxe2x80x2xe2x80x94CH2CH2xe2x80x94Oxe2x80x94(CH2CH2O)11xe2x80x94H, C9H19xe2x80x94C6H4xe2x80x94Oxe2x80x94(CH2CH2O)50xe2x80x94H, other nonionic surfactants, and combinations thereof. Examples of cationic surfactants include, but are not limited to Rfxe2x80x2xe2x80x94CH2CH2SCH2CH(OH)CH2N(CH3)3+Clxe2x88x92, other cationic surfactants, and combinations thereof. Examples of anionic surfactants include, but are not limited to, C12H25(OCH2CH2)4OSO3xe2x88x92NH4+, C12H27xe2x80x94C6H4xe2x80x94SO3xe2x88x92Na+, other anionic surfactants, and combinations or two or more thereof. In each of the formulae, Rfxe2x80x2 is a perfluoroalkyl group generally having about 3-18 carbon atoms. The preferred surfactants are nonionic surfactants having polyethylene glycol in the molecular chain.
The quantity of the fluorocarbon silane or its hydrolysis product in the aqueous emulsion can be any effective amount to produce desired heat resistance and water repellency. Generally, it can be about 0.1 to about 30 weight %, preferably 2 to 20 weight %, and more preferably 7 to 15 weight % based on the total weight of the emulsion.
The weight ratio of the fluorocarbon silane to the surfactant can be any ratio that can exhibit the desired emulsion property and can be about 1:1 to about 10:1, preferably 5:1 to 2:1, and more preferably 10:3 to 10:4.
The pH of the substantially aqueous emulsion can be adjusted to either 4.5 or lower, or 7 or higher. Generally an acid such as phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid, acetic acid, or formic acid can be used to adjust the pH to 4.5 or lower. Phosphoric acid is preferred because a coating layer formed by spreading the emulsion of which the pH is adjusted with phosphoric acid can prolong the heat resistance and the water repellency.
A basic material such as ammonia, pyridine, and sodium hydroxide can be used to adjust the pH to 7 or higher.
The aqueous emulsion can include ordinary additives such as pigment, sterilizer, ultraviolet absorbent, and antioxidant in the range where they have no influence on the stability of the emulsion and the heat resistance and water repellency of the emulsion or a coating layer containing the emulsion.
Any means known to one skilled in the art can be used to produce the emulsion disclosed herein. However, it is preferred to contact or dissolve a surfactant in water followed by adding a fluorocarbon silane, adding any above-disclosed additive(s) as desired or needed, adjusting its pH as desired, and adding a silicon-containing compound to it.
Also, in order to suppress the self-condensation of the fluorocarbon silane and to maintain it in a hydrolyzed state, it is preferable to add the fluorocarbon silane after dissolving the surfactant. It is also preferred to slowly add a fluorocarbon silane while stirring by any ordinary stirring means known to one skilled in the art.
The undercoat layer can be formed by applying such as, for example, spreading or spraying an undercoat solution onto the base material followed by drying by any means known to one skilled in the art. The undercoat solution can contain at least one film-forming agent such as silicon dioxide, titanium dioxide, zirconium dioxide, organoalkoxysilane, polysilazane, and combinations of two or more thereof.
According to the invention, a heat-resistant and water-repellent coated product is also provided. Generally it is a substrate or base material having thereon a coated layer comprising the emulsion. The coated layer is on the surface of the substrate. The term xe2x80x9csubstratexe2x80x9d is exchangeable with xe2x80x9cbase materialxe2x80x9d.
The substrate can be any material. Because a heat-resistant and water-repellent coat layer is formed on the surface of the substrate, an excellent heat resistance and water repellency can be prolonged. Suitable substrates include, but are not limited to, metal plate such as aluminum and stainless steel, glass plate, ceramic tile, brick, concrete, wood, masonry, fiber, leather, plastics, and stone.
The surface on which the coating layer is formed is determined according to the shape and usage of the base material. For example, in a plate-shaped base material, the coating layer can be formed on one surface or both surfaces. In a metal part, the coating layer can be formed on the entire surface.
In the invention, an undercoat layer can be formed between the substrate and the emulsion layer. After forming the undercoat layer, an emulsion disclosed above can be applied to, such as spread on, the undercoat layer, so that the heat resistance and the water repellency can be prolonged. The undercoat layer can be one or more layers.
The undercoat layer can be formed by applying such as, for example, spreading or spraying an undercoat solution onto the base material followed by drying by any means known to one skilled in the art. The undercoat layer can comprise or is produced from a solution containing at least one film-forming agent such as silicon dioxide, titanium dioxide, zirconium dioxide, organoalkoxysilane, polysilazane, and combinations of two or more thereof. The film-forming agent can be the same as that disclosed above.
A solvent can be used in the preparation of the undercoat solution. A suitable solvent includes, but is not limited to, toluene, xylene, hexane, heptane, butyl ether, butyl acetate, acetone, and combinations of two or more thereof. The concentration of the film-forming agent in the solution can be in the range of from about 1 to about 100 weight % depending on the desired thickness of the undercoat layer, the type of film-forming agent used. The general concentration of the film-forming agent in the solution can be in the range of from about 10 to about 50 weight %.
The solution can be applied onto the base material by any known method such as dipping method, spray method, spin-coating method, and roll-coating method. Because it is often in demand that the undercoat layer be able to be formed on the glass base material without damaging the transparency, the dipping method is preferred to maintain the transparency.
Heating may also be applied to accelerate the drying process. Usually, the drying is carried out in a temperature range of 100-350xc2x0 C. for 5 minutes to 24 hours.
The coating layer of the substantially aqueous emulsion can be formed on the undercoat layer using the same method disclosed above. The above-disclosure of the emulsion is incorporated herein for the interest of brevity.
If desired or necessary, the base material on which the aqueous emulsion is spread can be washed with water after drying to remove the remaining surfactant.